This invention relates to the production of chloric acid, HOCl.sub.3, from hypochlorous acid. More specifically it relates to the filter press membrane cell apparatus utilized to electrolytically produce chloric acid in high current density operation. Chloric acid can be used in the formation of chlorine dioxide, a commercial bleaching and sanitizing agent.
Chloric acid is a known compound which has been made in laboratory preparations by the reaction of barium chlorate with sulfuric acid to precipitate barium sulfate and produce a dilute aqueous solution of chloric acid which was concentrated by evaporation of water under partial vacuum. In another methods sodium chlorate is reacted with an acid such as hydrochloric acid or sulfuric acid to produce an aqueous solution of chloric acid containing sulfate or chloride ions as impurities. In addition, commercial processes for producing chlorine dioxide form chloric acid as an intermediate.
U.S. Pat. No. 3,810,969 issued May 14, 1974 to A. A. Schlumberger teaches a process for producing chloric acid of high purity by passing an aqueous solution containing from 0.2 gram mole to 11 gram moles per liter of an alkali metal chlorate such as sodium chlorate through a selected cationic exchange resin at a temperature from 5.degree. to 40.degree. C. The process mole to about 4.0 gram moles of HOCl.sub.3.
Until the present time chloric acid, however, has not been produced or available commercially because of high manufacturing costs and because of concomitant undesired impurities formed with the chloric acid during its production. A way to efficiently produce chloric acid at substantially reduced costs has been discovered that appears to be commercially feasible. Prior chloric acid production routes have yielded impurities, such as alkali metal ions, chloride ions and sulfate ions. These problems are solved in the design of the present invention by providing a filter press membrane electrolytic cell that operates at high current density to produce concentrated high purity chloric acid that is stable at ambient conditions.